This invention relates to a new stabilizer composition for enhancing the resistance to deterioration upon heating of vinyl chloride polymers, and to vinyl chloride polymers having enhanced resistance to deterioration in initial color, heat stability and clarity as a result of incorporating therein a stabilizer composition according to this invention.
There is a voluminous literature on the stabilization of vinyl chloride polymers. Patent disclosures of materials stated to be useful in minimizing deterioration of vinyl chloride polymers on heating number well over one thousand. Among the more important heat stabilizers in commercial use are mild alkalis such as sodium carbonate, disodium phosphate, and sodium and potassium salts of partially esterified phosphoric acids; carboxylates and phenolates of zinc, cadmium, and the alkaline earth metals; inorganic and organic lead salts; organotin carboxylates, as disclosed by Quattlebaum in U.S. Pat. No. 2,307,157; organotin mercaptides as disclosed by Leistner in U.S. Pat. Nos. 2,641,588 and 2,641,598; various metal-free organic compounds such as the polyols, e.g. mannitol, sorbitol, glycerol, pentaerythritol, organic phosphites, 1,2-epoxides, e.g., soybean oil epoxide, isooctyl epoxy-stearate, and the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) propane, and nitrogen compounds, e.g., phenylurea, N,N'-diphenylthiourea, and 2-phenylindole. For detailed discussion of heat stabilizers for vinyl halide resins, reference may be made to the articles, L. I. Nass, in "Encyclopedia of Polymer Science and Technology" (N. Bikales, ed.) Vol. 12 pages 737 to 768 (1970); N. L. Perry "Barium-Cadmium Stabilization of Polyvinyl Chloride," Rubber Age 85 449-452 (June, 1959), and by H. Verity-Smith, British Plastics 27 176-179, 213-217, 307-311 (1954); the brochure by the same author The Development of the Organotin Stabilizer (Tin Research Institute, 1959) and the book La Stabilisation des Chlorures de Polyvinyle by F. Chevassus (Amphora, Paris, 1957).
There have also been disclosures of the effectiveness of certain phosphorus compounds having organic groups directly linked to phosphorus in stabilizing organic materials subject to various deteriorating influences. E. K. Bolton in U.S. Pat. No. 2,230,371 of Feb. 4, 1941 disclosed the incorporation in organic substances subject to oxidative decomposition catalyzed by copper and its compounds of small amounts of a phosphorus compound of the class of organic monophosphonic acids and organic dihydroxyphosphines, that is compounds having the organic radical directly attached to phosphorus and having two hydrogens replaceable by metal. In a direct comparison of an organic monophosphonic acid and its dodecyl ester (having only one replaceable hydrogen) in a gasoline oxidation induction period test, only the former compound was effective, thus demonstrating the critical requirement of two replaceable acidic hydrogen atoms in the molecule.
G. Denison Jr., in U.S. Pat. No. 2,346,155 of Apr. 11, 1944 disclosed a hydrocarbon oil containing a combination of stabilizing agents, comprising a thioether or seleno ether and an oxide, sulfide, or selenide having directly connected to an oxygen, sulfur or selenium atom both a metal in a basic form and an acid-forming element such as those of Periodic groups IIIA, IV, VB, and VIB. Denison's disclosure encompasses untold thousands of compounds in over 150 classe, of which 28 are classes of phoshorus compounds among which phosphonic acids and phosphonic acid monoesters are mentioned in the form of metal salts.
C. B. Havens in U.S. Pat. No. 2,959,568 of Nov. 8, 1960 disclosed haloethylen polymers stabilized with an inorganic salt of phenyl-phosphonic acid. In an example, an 85-15 copolymer of vinylidene chloride and vinyl chloride was heated at 178.degree. C. until the pressure of evolved hydrohalide gas evidenced thermal degradation. Nothing is disclosed about the effect if any on initial color or eventual color changes of any of Havens' phenylphosphonates. W. Leistner in U.S. Pat. No. 2,997,454 of Aug. 22, 1961 disclosed polyvinyl chloride compositions of excellent initial color stabilized with a combination of an organic triphosphite with a heavy metal fatty acid salt to which there is added a phosphorus compound having at least one hydrogen atom of acidic character. The phosphorus acids in Leistner's compositions are defined by the formula ##STR1## In this formula, phosphorus has a valence of three or five, the additional two valences being indicated by dotted line bonds. Typical phosphorus acids coming within this general formula are the following: ##STR2##
In the above formulae R.sub.1 and R.sub.2 represent an organic aliphatic, aromatic or nonaromatic alicyclic hydrocarbonor heterocyclic radical having from one to about thirty carbon atoms. R.sub.1 and R.sub.2 in I, II, III(a) and IV may be the same or different.
R. Harrington, Jr. in U.S. Pat. No. 3,274,014 of Sept. 20, 1966 disclosed yarn compositions of synthetic fibers having incorporated a small amount of a metal monoalkyl or monoaryl phosphate, metal dialkyl phosphate, metal alkyl phosphonate, metal alkyl (alkyl phosphonate) or metal dialkyl phosphite that are resistant to ultraviolet light. Examples show among others yarns spun from dopes of modified vinylidene chloride-acrylonitrile copolymer containing either zinc (ethyl phosphonate) or zinc bis(ethyl(ethyl phosphonate)).
J. Spivack in U.S. Pat. No. 3,310,575 of Mar. 21, 1967 disclosed metal derivatives of monobasic and dibasic hindered phenol substituted phosphonic acids that have thermal stabilizing properties for polymeric substances as well as rendering the polymeric substance more amenable to dyeing and reducing the tendency of the polymeric substance to discolor upon exposure to light, whether dyed or not. Spivack's phosphonate derivatives are characterized by the formula: EQU [P].sub.m M.sub.x [G].sub.p
wherein
M is a metal having an available valence of from 1 to 4; PA1 G is an anion having an available valence of from 1 to 3; and PA1 P is of the formula: ##STR3## and wherein z has a value of from 0 to 6, PA1 n has a value of from 0 to 1. PA1 z has a value of from 0 to 6; PA1 v has a value of from 1 to 4; and PA1 y has a value of from 1 to 4, the value of v being the same as the available valence of M. PA1 M is a divalent metal which may be cadmium, barium, calcium or zinc.
y has a value of from 1 to 4, PA2 m has a value of from 1 to 3, PA2 x has a value of from 1 to 2, and PA2 p has a value of from 0 to 3, PA2 n,m,p and x being so selected as to satisfy the expression ##EQU1## wherein r is the valence of anion G and has a value of from 1 to 3.
The group M consists either of a metal in full free valence state such as sodium, cadmium, zinc, barium, nickel, aluminum, tin, chromium, cobalt, iron, copper, titanium, vanadium, and the like, or of a metal derivative in which part but not all of its full free valence state is satisfied by alkyl substitution, e.g. dialkltin. Preferably M is a metal in its full free valence state, particularly those having a valence of 2 to 4 such as cadmium, zinc, barium, nickel, iron, copper, aluminum, tin, chromium, titanium, vanadium, and cobalt. Of these, aluminum and the transitional metals, particularly nickel, are especially useful.
The available valence bonds of the metal will be satisfied by one or more phosphonate or O-alkyl phosphonate groups and, if needed, by anions, organic or inorganic. Thus when n=0, there may be one (m=1) or more (m=2 or 3) phosphonate groups. Likewise there may be one or more O-alkyl phosphonate groups (n=1). In some instances, as in the case of aluminum or chrominum, three phosphonate groups combined with two metal atoms (x=2) to satisfy the valence requirements. In the case of mixed salts, one, two or three monovalent anions will make up the valence requirements. In all instances, the compounds will contain at least one phosphonate group or at least one O-alkyl phosphonate group and the values of n,m,p and x is such that the following expression is satisfied: ##EQU2## wherein r is the valence of anion G and has a value of from 1 to 3.
The anion G may be organic or inorganic. Illustrative of such organic anions are carboxylate, such as those derived from carboxylic acids containing from 1 to 30 carbon atoms, preferably 2 to 18 carbon atoms, e.g. acetate, laurate, stearate, benzoate, malonate, maleate, succinate, and the like; phenates and alkyl substituted phenates; alkyl- and aryl-sulfates and -sulfonates; alkyl- and arylphosphates and -phosphonates; and inorganic anions such as chloride, bromide, iodide, fluoride, nitrate, cyanide, cyanate, thiocyanate, sulfate, and the like.
A. DiBattista in U.S. Pat. No. 3,824,192 disclosed as part of a multicomponent stabilizer system containing a phenolic antioxidant, a sulfur compound synergist, an ultraviolet light absorber, and a benzoate type co-light stabilizer, an organophosphorometal compound that is either Spivack's above hindered phenol substituted metal phosphonate derivative or a metal and metal complex salt of a hindered phenolic alkylphosphinic acid represented by the formula ##STR4## wherein M is a metal or metal complex cation, this cation having an available valence of from 1 to 4;
Disclosures are also acknowledged of stabilizer compositions including metal derivatives of organic phosphorus compounds having no direct carbon to phosphorus linkage. P. Klemchuk in U.S. Pat. No. 3,219,605 of Nov. 23, 1965 disclosed that cadmium, barium, calcium, or zinc salts of monoalkyl phosphites are remarkably effective light stabilizers for polyvinyl chloride compositions, alone or in combination with other light and/or thermal stabilizers. The metal salts are defined by the formula ##STR5## wherein R is an alkyl radical, e.g. alkyl having from 1 to 30 carbon atoms, preferably having from 1 to 12 carbon atoms, and
Farbwerke Hoeschst in French Pat. No. 1,412,321 of Aug. 16, 1965 disclosed the stabilization against light of polyvinyl chloride with 0.1 to 5% by weight of nickel organic phosphites containing only nickel, phosphorus, carbon, hydrogen and oxygen, along with barium-cadmium soaps, organic phosphite, epoxy compounds, and optionally ultraviolet absorbers.
T. Kamijo in U.S. Pat. No. 3,312,658 of Apr. 4, 1967 disclosed a stabilizer combination of alkyl-substituted phenolic antioxidant with a synergistic agent which is a nickel salt of a monoester or diester of phosphoric acid, represented by one or both of the formulas: ##STR6## where the R radicals are selected from the group consisting of alkyl, aryl, alkaryl and cycloalkyl radicals.